The present application relates to a data unit processing entity in a data unit transmission network and to a control method for such a data unit processing entity.
In the field of data communication, it is known to provide data unit transmission networks. Data that needs to be transported over such a data unit transmission network is divided into individual data units, and each data unit carries a routing address that is used by network nodes for sending the data unit to its intended destination. The handling of such data units is typically performed in accordance with an appropriate protocol, e.g. the Internet Protocol (IP). It is noted that such data units may carry different names in the context of different protocols, such as packet, protocol data unit, segment, frame, etc. In the present description and claims, the term “data unit” is used generically to describe any such fragment of data that is being transported over an appropriate network.
If all network nodes of a data unit transmission network are immobile and are always connected to the overall network via the same links, then there is no problem in routing data units to intended receiving nodes, because the routing address serves both to identify and to locate the receiving node. However, the situation becomes more complicated if at least some nodes that can access the data unit transmission network over more than one link. For example, a node could be capable of moving and of accessing the network over various links depending on location. Such a node capable of accessing the network over more than one link will therefore be referred to as a mobile node in the present description and claims. However, it is to be noted that the term “mobile node” relates to any node capable of accessing the network over more than one link, regardless of whether the node is in fact physically mobile. In other words, the term “mobile node” also covers nodes that are neither physical mobile nor moving, as long as they are capable of accessing via more than one link. As an example, a mobile node could therefore be a stationary computer that is equipped with a wire line LAN connection, a wireless LAN capability and a GPRS radio capability, such that it could access a network (e.g. the Internet) over these three different links.
The situation of nodes that can access a network over more than one link requires additional routing capabilities.
In connection with work on expanding the capabilities of the Internet protocol, request for comments 3220 that relates to version 4 of the Internet Protocol (IPv4) describes the use of two types of routing addresses, a so-called home address for identifying a node and a so-called care-of address for forwarding of data units to mobile nodes. The home address (HoA) is an example of the general concept of an identifying address (IA), and the care-of address (CoA) is an example of the general concept of a forwarding address (FA).
The term “mobile node” therefore refers to such that nodes that can have a plurality of forwarding addresses simultaneously.
In a generalised network operating in accordance with an appropriate routing protocol (RP), the network nodes are arranged to distinguish between the IAs and the FAs in a data unit to be forwarded. It is noted that the term “routing protocol” (RP) as used in the present description and claims is generic to describe any protocol suitable for allowing the routing of data units over a plurality of network nodes. IP is an example of such a general routing protocol.
In a data unit transmission network that uses identifying addresses and forwarding addresses, one may provide special data unit processing entities or agents that perform a decision operation for determining a forwarding address on the basis of an identification address. It is noted that the term “entity” or “agent” as used in the present specification and claims refers to a functional element that is capable of performing a certain function. An entity or element may be located in a single place, e.g. in a node, but it can also be distributed over several locations, e.g. several nodes or other network elements.
The data unit processing entity of this type comprises a decision part for setting a forwarding address in a received data unit depending on the identification address set in the received data unit, by accessing a memory that contains decision data, where the decision data comprises one or more forwarding addresses associated with identification address. As an example, in the present proposals for developing IP, i.e. for version 6 (IPv6), the use of a so-called home agent is proposed. A home agent receives data units that contain the home address (i.e. the identifying address), and on the basis of rules and parameters stored in a so-called binding cache performs a so-called binding operation, i.e. determines the care-of address for the given home address. In the present discussion of further developing IP networks using mobile nodes, i.e. in the discussion for Mobile Ipv6 (MIPv6), it is considered that the mobile node can have multiple care-of addresses. It can re-route between different care-of addresses by indicating to appropriate agents in the network which care-of address to use.
The method of managing the decision data is performed by letting the mobile node send so-called binding updates to the home agent or to the so-called corresponding nodes. A corresponding node is a node with which the mobile node is in communication, and in the course of this communication, the mobile node can simply indicate to the corresponding node, which care-of address to use. The basic principle is that the home agent and corresponding nodes can only have one care-of address listed in the binding cache. It is the mobile node that decides to which care-of address data is directed that is destined for the home address (via the home agent), and it can determine for each corresponding node to which care-of address the corresponding node should send. The principle therefore is that each home agent or corresponding node only has one of the possible care-of addresses indicated in its binding cache.
In connection with mobile Ipv6 a system called NOMADv6 has been proposed, which comprises filters for mobile Ipv6 bindings. NOMAD allows a mobile node that has a plurality of care-of addresses to register multiple binding updates at any appropriate binding agent (e.g. home agent, correspondent node or a so-called mobility anchor point) and associate these different bindings with a filter. The filter allows to direct different flows to different care-of addresses based on the Traffic Class field in the IPv6 header, the Flow Label field in the IPv6 header, the Protocol Extension field in the IPv6 header, which identifies the type of higher layer protocol being used, the Source Address (or source address prefix), a range of Source Port or Destination Port numbers in the protocol header, or the value of a certain data region within the IPv6 packet.
A further concept known in connection with mobile IPv6 is the use of bicasting, i.e. of allowing a home agent to temporarily have bindings to two care-of addresses for the same home address. While such bindings are simultaneously active, every packet is replicated and a copy is sent to each care-of address.